1. Field of the Invention
The present invention relates to means for separating a light particulate material from a heavier particulate material in a mixture. The present invention even further relates to means for removing one material from a mixture using an apparatus having an adjustable flow through area therein in combination with an upwardly flowing gas stream to entrain the lighter particles in the upwardly moving gas stream and allow the passage of the heavier particles downwardly through the adjustable flow through area.
2. Description of the Prior Art
In the mass production of products utilizing botanical materials, such as tobacco for tobacco products, removal of other particulate materials from the botanical material generally results in a large or substantial amount of waste. In an industry such as the tobacco industry, the botanical components of a salable product is increasingly expensive and it is therefore necessary to recover as much of the tobacco as possible in a sand removal step of the process.
In the separation of botanical fines, such as tobacco from sand, the botanical material is much lighter than the sand and two methods of separating the components have been suggested and utilized. One method utilizes the different absorption characteristics of the two components in a heavy liquid medium. Techniques of this type have been somewhat limited in that there must be a subsequent separation of the desired botanical material from the medium affecting the separation. Where the medium carrying out the separation is a liquid, a further consideration must be made as to the effect of the liquid medium on the botanical material. Furthermore, this separation of the botanical material from the liquid may also present relatively complex problems.
U.S. Pat. No. 3,842,978 teaches an apparatus where botanical materials are separated from sand by their different response to a flowing air stream passing through a vibrating array of particles. The separation of the botanical material from the sand is carried out on a porous array having a flowing stream of gas passing up through the array. The separation is primarily controlled by the configuration and packing density of particles comprising the array and the velocity of gas passing therethrough. This type of device is rather complex, and is mechanically unsuited for many applications.